"He had us fooled in the most beautiful way," Michael Diamond said of Adam Yauch, his friend and fellow Beastie Boy for more than 30 years, describing the latter's "incredible optimism" during his three-year battle with cancer. "I believed, up to last week, that Adam was somehow coming back," Diamond confessed, in a long, frank interview after Yauch's death on May 4th. "But I wouldn't trade that optimism for anything," he added quickly, sitting in the kitchen of his Brooklyn home, only six blocks from the house where Yauch grew up. "Because the other option is no fun."

Did Yauch always have a fighter's spirit?He had this tenacity and faith before he discovered Buddhism. His mom said that was already there. No matter how straight-up nuts an idea was, he had the ability to follow through on things he believed in. Like the cover of Paul's Boutique: "A 360-degree photo? You can't have a camera spin around." He researched it and found one. It was an innate thing for him.

As a rapper, Yauch had a unique, raspy baritone. He sounded more like a soul singer.Even when we were doing our first hip-hop records, when we were 19 and 20, he sounded like a gruff 40-year-old. He was the Bobby Womack of rap.

Yauch was a gifted MC. It was his flow on things, rather than specific lyrics, that first blew Adam [Horovitz] and I away. Early on, we were in the studio, amazed by how Yauch made it seem so effortless. Horovitz and I were maybe a little jealous. And Rick [Rubin] said to me, "No, this is good. This is where Yauch is at. You sound like you're working hard. You're the working rapper. [Laughs] I'm still not sure what to take away from that.

What were your first impressions of Yauch when you met as teenagers?Adam taught me the ropes – how to make my own [punk-band] badges, how to fake [hand] stamps to get into shows. And after he, [original Beastie Boys guitarist] John Barry and I saw Black Flag at the Peppermint Lounge, Yauch said, "We're starting a band, and you two guys are in it." It was the same energy that enabled him to start his film company, Oscilloscope – the ability to will something to happen.

What's an example of that on Licensed to Ill?We were playing around with this 808 drum machine. We had this beat, and Yauch said, "I'd like to hear what it would sound like backwards." Run from Run-D.M.C. was there, and he was like, "Man, this is crazy." But Yauch recorded this beat, bounced it to another tape, flipped it around – this is pre-digital sampling – and bounced it back to the multi-track tape. The reversed beat basically became "Paul Revere." Yauch saw this thing we couldn't see – and he killed it.

He talked about experimenting with acid during the time of Paul's Boutique.Yauch was starting this inward mind journey. We were layering a lot of samples on top of each other, and Yauch was definitely pushing that. The acid experience gave him the ability to see, "Wow, this is great – press 'play' on everything at the same time." Yauch was great at lacking fear.

Did his personality change after he became a Buddhist?He abandoned the band for months in the winter to go snowboarding, on this very serious level. Then it wasn't snowboarding. He would disappear for two months of teaching by his Holiness the Dalai Lama in Dharamsala. He gradually incorporated that into the music. He was the first to realize we had this soapbox, and we needed to do something with it.

But he was never dogmatic about it. He'd say, "You should see these monks. They love playing practical jokes on each other." When we were smashing cars in the "Sabotage" video, it was the same thing. We just did it with mustaches and wigs.

How much music did you make at your final recording session with him last fall?Adam instigated it. It could only come from him, in terms of where he was at with treatment. It was stuff we had written or demo-ed, and there were new ideas. He wasn't sure he was able to do vocals. But after a bit, we ended up doing them. And he was fine. It was a way for him to say, "Yeah, I'm doing it."

Can you imagine making music without him?I can see making music. I don't know about a band format. But Yauch would genuinely want us to try whatever crazy thing we wanted but never got around to.